The effect of the antibiotic tetracycline on the growth and photosynthetic activity of the diatoms Cyclotella caspia Grunow, 1878, and Thalassiosira weissflogii (Grunow) G.A. Fryxell & Hasle, 1977, has been studied. The rate of tetracycline concentration decreases in the medium with and without has been estimated. The expediency and prospects of using diatoms as promising objects for water purification from tetracycline are shown. It was found that the rate and efficiency of tetracycline removal from the medium in the presence of algae depends on the initial content of the pollutant in the medium. The maximum efficiency of antibiotic removal is observed at concentrations of the pollutant provoking the hormesis growth of algae at 5 mg/L in C. caspia and 10 mg/L in T. weissflogii. In samples with C. caspia and tetracycline, the residual antibiotic content in the medium was 10-14% lower than in samples without algae. In the experiment with T. weissflogii, this indicator reached 15-16%. At concentrations of the pollutant, 2 and 10 mg/L in C. caspia and 2 and 5 mg/L in T. weissflogii, the effectiveness of removing the antibiotic by algae was lower. The residual content of tetracycline in the medium was on average 8-11% lower than in samples without algae. At antibiotic concentrations of 15 and 20 mg/L, the rate of its removal in samples with and without algae did not significantly differ. This result is obviously due to the toxic effect of tetracycline on cells, leading to pronounced inhibition of algae growth and/or death.

Department of Algae Ecological Physiology A O Kovalevsky Institute of Biology of the Southern Seas of the Russian Academy of Sciences 2 Nahimov Ave Sevastopol Russian Federation

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